The present invention relates to a monolithic integrated circuit with several capacitors form serve a bypass to ground.
More particularly, it relates to such a monolithic integrated circuit in which each capacitor is composed of two coatings located on a substrate and separated by a dielectric layer, wherein a lower coating located on the substrate under the dielectric layer is contacted with a ground conductor on the opposite substrate side.
Such a construction of monolithically integrated capacitors is known from xe2x80x9cDesign Guide, Gas Foundry Servicesxe2x80x9d of Texas Instruments Version 4.2, February 1997, pages 1-7.
In a monolithically integrated microwave circuit xe2x80x9cMMICxe2x80x9d, conventionally a highest possible packing density of the individual switching elements is desired. When in a circuit several capacitors which form a bypass to ground are provided, then due to the ground connections of the capacitors through contactings in the substrate a relatively great distance between the capacitors is maintained, since with a small distance of the through contacting the substrate has a tendency to break. The minimal permissible distances between the through contactings are also relatively great since the diameter of the through contactings conically increases toward the substrate lower side provided with the ground conductor, which is inavoidable for production of the through contactings from technological reasons. Circuits with several capacitors which form a bypass to ground, for example such as disclosed in IEEE Transactions on Microwave Theory and Technique, volume 45, No. 12, December 1997, page 2256-2260 require an amplifier circuits for blocking of high frequency signals relative to bias voltage circuits.
Accordingly, is an object of present invention to provide a monolithic integrated circuit with several capacitors forming a bypass to ground, in which the capacitors can be arranged relative to one another at smallest possible distances.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a monolithic integrated circuit, in which the lower coatings of the capacitors are connected with one another, and the lower coating which belongs to only one capacitor is connected to a through contacting in the substrate with a ground conductor.
In the monolithic integrated circuit designed in accordance with the present invention, no longer for each individual capacitor a single through contacting must be provided, whereby the minimal permissible distances between the capacitors are substantially reduced.
In accordance with a further feature of present invention it is advantageous to form the lower coatings of all capacitors from a single lower coating. Moreover, it is advantageous when for capacitors which are dimensioned for different frequency regions, the through contacting for such capacitors is provided which is dimensioned for a higher frequency region than other capacitors.
Preferably, the circuit of several capacitors which form a bypass to ground can be used in a amplifier circuit for blocking high frequency signals relative to a bias voltage. For this purpose two capacitors which form a bypass to ground are connected parallel, wherein one of the both capacitors for high frequency signals in the operational frequency band of the amplifier and the other capacitor for high frequency signal below the operational frequency band form a short circuit to ground.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.